Although there is wide consensus on the theory that the moon formed through the collision of Earth and another object, the specifics of that theory are still not certain. And two new papers published in Science present two new significantly different takes on those specifics.

Saturn’s moon mix—different locations, different densities, some are ice, others rocky—begs the question how did they form. Current research by Erik Asphaug and Andreas Reufer provide a possible answer:

According to a model proposed by Erik Asphaug, a planetary scientist at the University of California, Santa Cruz, and his colleague Andreas Reufer of the University of Bern in Switzerland, Saturn and its satellites initially resembled a miniature version of the Jupiter system, with four large satellites similar in size to Jupiter’s Galilean moons. Saturn’s satellites then began to merge, eventually forming Titan, the planet’s largest moon, says Asphaug, who presented the model on 17 October at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Reno, Nevada.

The mid-size satellites would have formed from the scraps left over from building Titan, with the mergers perhaps accounting for Titan’s surprisingly elongated orbit. The merging may have been triggered by an instability in the Solar System about 3.8 billion years ago, when theorists think that the orbits of Uranus and Neptune were migrating. Because of Jupiter’s bigger gravitational grip, its moons were relatively impervious to the disturbance, Asphaug speculates.

My latest article is about new research that adds to the uncertainty of how the Moon was formed by looking at the Moon’s isotopic composition:

Question over theory of lunar formation

A chemical analysis of lunar rocks may force scientists to revise the leading theory for the Moon’s formation: that the satellite was born when a Mars-sized body smacked into the infant Earth some 4.5 billion years ago.

If that were the case, the Moon ought to bear the chemical signature of both Earth and its proposed ‘second’ parent. But a study published today inNature Geoscience1suggests that the Moon’s isotopic composition reflects only Earth’s contribution.

Science Writer

Award-winning science writer with a passionate interest in the intersection of popular culture and the physical sciences. Articles include features and news stories on the earliest known recorded sounds, an essay on Hubble Space Telescope photography and evidence suggesting the universe is a hologram.

Dubbed “the scoop machine,” by the Knight Science Journalism Tracker, Ron has been published in National Geographic, Nature, The New York Times, Science, Science News, Scientific American, and US News & World Report.